Modified Washington with unstable clarifier

[Enterprise312ok]

A freind of mine brought me a Uniden Washington modified with 2 crystals on the bottom of the board for extra channels, also an open clarifier. The clarifier works perfect on startup but after about 5 min of warmup the frequency drifts up to 27.**54 or 400 cycles high and the clarifier will not decrease the frequency only increase.

Hopefully one of You great techs has encountered this issue before

 

[brandon7861]

It could be a worn potentiometer. It could also be from making wires longer (thought I posted that). I remember mine acting up before I put it in the shed.

Mine also had the clarifier open, and I never had an issue until I extended the wires on something (i think the channel mod switch). I'd have to go look in the shed to see what I did, but I remember once I made those wires longer to move the switch, mine did what I remember to be the very same thing. Maybe the extra wires causes some other resonance (like one of the spurious responses in the crystal).

 

[Captain Kilowatt]

I'm highly suspect of the two extra crystals. If the wires are long or not tidy, they will introduce stray capacitance and detune the crystals. I had to install separate trimmer capacitors to pull the crystals back on frequency when I did a frequency mod involving extra crystals and had to keep the crystal leads REALLY short.

 

[Enterprise312ok]

This one is modified with two crystals soldered directly to bottom side of board and a trimmer. Doing some on air testing I have found that it is only the transmit that is going off frequency the clarifier is always working on receive but after warm up the transmit drifts 500hz up from center frequency and cannot be adjusted back down with clarifiet, only up.

 

[Enterprise312ok]

Here are the photos of the mod. Maybe swaping out the wires for small coax will help

 

[Enterprise312ok]

there is also a long wire going from the board with the three buttons to the squealch knob that turns on the mod when switched to pa mode. According to the locals around here this is how "Snuffy" did all the washingtons he sold.

 

[AxlMyk]

I don't like the wires going through the chassis holes like that.

 

[Enterprise312ok]

I don't like the wires going through the chassis holes like that.

For infuctance issues or for chafing? I wonder if some small ferrite beads wold help.

 

[AxlMyk]

Chafing. The wires could lay over the edge and be zip tied using the holes.

 

[Enterprise312ok]

I went ahead and removed the homemade channel kit and realigned the radio and the instability has been resolved.

 

[nomadradio]

Rock on! Long wires and crystals just don't play well together. Any factory setup that selects multiple crystals will use diodes or transistors to do the actual switching. That way the long wires to the front panel are carrying only DC current, isolated from the oscillator circuit and the crystals. Sometimes a tweaknician gets away this this kind of lashup, but not often.

73

 

[Enterprise312ok]

I spoke too soon, the clarifier instability is back. I am going to get that circuit back to stock tomorrow morning.

 

[brandon7861]

Back in post #2, I too thought I had it figured out, but the problem returned after shortening the wires. When this thread was revived, I decided to take a look at mine again. I though this time that the crystals on the channel mod switch needed gounding, so I did that and decided to try an alignment.
And thats when I found it. Touching the trim cap for the 10.24MHz (edit: 11.1125MHz) made it jump. Check this out! I knew those caps had a short turns lifetime, but I never seen one go bad before.

 

[Xracerx13]

Is the clarifier unlocked? If so, where is the 8v coming from?

 

[nomadradio]

Any chance the EXPO kit's switch is getting noisy? A shot of cleaner might help. A noisy switch in line with a crystal will cause instability.

73